1. Field of the Invention
The present invention relates generally to a mobile terminal, and more particularly to a dual-mode mobile terminal supporting both synchronous and asynchronous modes.
2. Description of the Related Art
Recently, the use of mobile terminals has rapidly increased around the world. Mobile communication systems, which provide communication services to the mobile terminals, are generally divided into a global system for mobile communication (GSM) mobile communication system, which is primarily used in Europe, and a Code Division Multiple Access (CDMA) mobile communication system, which is primarily used in North America. The CDMA mobile communication system utilizes a synchronous data transmission mode and the GSM mobile communication system utilizes an asynchronous data transmission mode. The synchronous mode synchronizes a transmitter and a receiver using an American GPS satellite, whereas the asynchronous mode synchronizes the two using a special chip or software.
In the synchronous CDMA mobile communication system, a CDMA mobile terminal obtains accurate current time for synchronization. In the asynchronous GSM mobile system, a GSM mobile terminal cannot obtain accurate current time, such that the GSM mobile terminal must receive a current time that is adjusted and input by the user, and uses a clock generator to update and display the current time as time passes.
In some areas, both the synchronous CDMA mobile communication system and the asynchronous GSM mobile communication system provide mobile communication services. Conventionally, in such areas where the CDMA and GSM mobile communication systems are used together, users needed to have CDMA terminals if they wished to receive CDMA services or GSM terminals if they wished to receive GSM services. Recently, however, a dual-mode mobile terminal, which can access both the synchronous CDMA and asynchronous GSM mobile communication systems has been developed.
When the dual-mode mobile terminal is in the synchronous CDMA mode, the terminal can accurately display current time because it obtains accurate current time for synchronization. However, when the dual-mode mobile terminal is in asynchronous GSM mode, because the terminal receives current time adjusted and input by the user and uses the clock generator to update and display the current time as time passes, the terminal cannot accurately display the current time if the terminal receives incorrect time information from the user or if the clock generator malfunctions.